3&#39;-substituted-3, 5-diiodothyronine and salts thereof



United States Patent Office Patented Sept. 15, 1964 3,149,1533'-SUBSTiTUTED-3,5-DHODOTHYRONINE AND SALTS THEREOF Benjamin Blank,'Irevose and James F. Kerwin, Broomall, Pa., assignors to Smith Kline 8:French Laboratories, Philadelphia, Pa., a corporation of Pennsylvania NoDrawing. Filed Dec. 5, 1961, Ser. No. 157,249 8 Claims. (Cl. 260--519)This invention relates to novel thyromimetic agents having a basic3'-alkylated-3,S-diiodothyronine structure. More specifically thecompounds of this invention have very potent pharmacodynamic activitysuch as in increasing the basal metabolic rate in hypothyroidconditions, inhibiting the thyrotopic hormone, treating goiter anddecreasing the cholesterol content of the blood. The calorigenicactivity of these compounds is unexpectedly pronounced.

The basic structure of the compounds of this invention is represented bythe following formula:

Formula I in which R is alkyl of from 2 to 7 carbon atoms or phenyl. Theterm alkyl as used here denotes all possible alkyl groupsstraight,branched or cyclic such as cyclohexyl or cyclopentyl.

The preferred compounds are represented by Formula I when R is abranched chain acyclic alkyl group of from 3 to 7 carbon atoms. Thepreferred and advantageous compound of this invention is represented byFormula I when R is isopropyl, particularly in the L-series.

This invention also includes nontoxic, pharmaceutically acceptable saltsof the amino acids of Formula I formed either through the acid functionwith cations such as ammonium, lower alkylated ammonium or alkali metalions, for example potassium, sodium or calcium ions, or through theamine group with pharmacologically inert strong organic or inorganicacids such as hydrochloric, sulfuric or ethanedisulfonic acid. The saltsare formed by methods known to the art such as by dissolving the parentamino acid in a dilute aqueous solution of the acid or base with heat ororganic solvent then cooling to separate the salt.

The formulas used herein may be in the form of either DL, D or Lisomers. When no designation herein is used any of these isomers canequivalently be present. The DL-mixtures are often preferred because ofease of preparation. If pure biological activity is desired theL-isomers are particularly potent as calorigenic agents while the D-isomers are particularly potent as cholesterol lowering agents.Generally speaking the L-isomers are preferred.

The compounds of this invention have surprising activity being the onlythyromimetic compounds known to the applicants to date which have signficantly more thyrornimetic activity than has the commercial product,liothyronine (L-3'-3,5,-triiodothyronine). For example, L-3'-isopropyl3,5 -diiodothyronine of this invention is more than twice as active asliothyronine in the standard calorigenic test.

The fact that the compounds of this invention which have no iodinesubstituent in the phenolic ring of thyronine but rather are substitutedby higher alkyl groups are the most active thyromirnetics known to dateis even more surprising when the prior art is considered.

The prior art compounds closest to those of the applicants areDL-2-isopropyl-3,S-diiodothyronine of Zenker et al., J. Am. Chem. Soc.,81, 4643 (1959), and DL-3- methyl-3,5diiodothyronine of Pittman et al.,Endocrinology, 68 (2), 21.8 (1961).

The DL-2-isopropyl compound of Zenker et a1. is only 5% as active asliothyronine in the calorigenic test. [see J. Biol. Chem. 235, 1732(1960)]. The DL-3'-isopropyl- 3,5-diiodothyronine of this invention isat least 17 times more active than the Zenker compound which is for allpractical purposes inactive. The L-3'-isopropyl compound is at least 40times more active.

The DL-3'-isopropyl compound of this invention has been found to be 250times more active as a hypocholester-olemic agent thanDL-3-methyl-3,S-diiodothyronine reported by Pittman et al. TheDL-3'-ethyl compound is about times as active as the prior art 3-methyl.It is apparent that the closest related prior art compounds are, for allpractical purposes inactive while the higher alkylated compounds of thisinvention are extremely potent and useful compounds with no untowardsigns of toxicity.

The compounds of this invention are prepared by the following generalsynthetic methods starting from the known 3-alkyl-4-lower-alkoxyphenols(Method A) or from the known Z-alkyl loWer-alkoxybenzenes (Method B.

METHOD A oon tosyl chloride pyridine I NHAc NHAc + no-Q-ompn-oorm In theabove processes other variations of the reactions and intermediatesdescribed will be apparent to those skilled in the art. The term Acrepresents acetyl. All starting materials are known to the art. Theprocesses to the ether ester intermediates (Formula II) are similar tothose known to the art. These compounds are then converted to thedesired amino acids of Formula I by treatment with an excess of constantboiling hydriodic acid diluted with acetic acid. The reactionadvantageously is carried out at elevated temperatures of from about 60C. to the boiling point of the mixture for from about 30 minutes toabout 6 hours. Other variations of these reaction conditions have provedto be of little advantage. The reaction mixtures are worked up byqu'enching'in ice water, neutralizing with alkali and filtration of theseparated product. The compounds of this invention are used to treat theabnormal conditions outlined herebefore necessarily combined with apharmaceutical carrier such as lactose, talc, ethylcellulose, glycerinmonostearate, hydrogenated castor oil, etc. in a dosage unit adapted forinternal administration in the form of a capsule, tablet, suppository,aqueous suspension, etc. In certain skin disorders a lotion or ointmentform is desirable. The dose per dosage unit may vary widely as to thecondition being treated and the weight of the patient but a range fromabout 0.5 to about 100 mcg. is particularly useful. A typical dailydosage regimen would be from 1 to about 200 mcg. Of course, conditionssuch as a marked increase of BMR or heart rate would warn of overdosingand warrant reducing the intake of drug. For use as ahypocholesterolemic agent compounds having less calorigenic activity forexample the D-isomers may be used in somewhat higher doses than thosedescribed above.

Variations of this invention will be apparent to one skilled in the artsuch as other substitutions on the basic nucleus of this invention. Thefollowing examples are designed to make the practice of this inventionfully apparent.

' 7 Example 1 (METHOD A) A solution of 14.2 g. (0.041 mole) ofN-acetyl-3,5- dinitro-L-tyrosine, ethyl ester (Clayton J. Chem. Soc.,1951, 2472) in 90 ml. of dry pyridine is stirred while 8.03 g. (0.042mole) of p-toluenesulfonyl (tosyl) chloride is added. After heating onthe steam bath for 10 minutes the mixture is mixed with a solution of7.0 g. (0.042 mole) of 3-isopropyl-4-methoxyphenol in 10 ml. ofpyridine. After heating at reflux for 1.5 hours, the mixture isevaporated under reduced pressure to remove the pyridine. The residue istaken up in chloroform. After washing, the dried organic extracts areevaporated to give an oily residue which crystallizes from ethanol, N-acety1-3-[4-(4-methoxy-3-isopropylphenoxy) 3,5 dinitrophenyH-L-alanine,ethyl, ester, M.P. 107-109 C.

This compound (9.6 g., 0.0195 mole) together with 2.3 g. of 10%palladium-on-charcoal and 200 ml. of acetic acid is hydrogenated at lowpressure for about 30 minutes. The filtered reaction is added dropwiseto a cooled solution of nitrosyl sulfuric acid (prepared from 100 ml. ofacetic acid, 300 ml. of sulfuric acid at 60- 70 C.) at 0 C. Afterstirring an hour at 0 C. the mixture is added to a stirred mixture of41.5 g. of sodium iodide, 33.2 g. of iodine, 800 ml. of water and 500ml. of chloroform. The mixture is stirred at room temperature for 2hours and the organic layer separated. "After washing, the dried organiclayer is evaporated to give N-acetyl-3-[4-(4-methoxy-3-isopropylphenoxy)-3 ,5 diiodophenyl]-L-alanine,ethyl ester, M.P. 128-130 C. from ethanol.

A mixture of 7.5 g. (0.0115 mole) of this compound, 50 ml. of constantboiling hydriodic acid and 65 ml. of acetic acid is heated under refluxfor 3 hours. The mixture is poured into several volumes of ice water,then adjusted to pH 5-6 with 10% sodium hydroxide. The cooled mixture isfiltered to give a pink precipitate which is recrystallized from ethanolcontaining a small amount of hydrochloric acid by the addition of anequal volume of water and hot 2 N sodium acetate to give the desired L-3'-isopropy1 3,5 diiodothyronine hernihydrate, M.P. 225-226 .Q

Example 2 (METHOD B) A mixture of 59.3 g. (0.32 mole) ofo-cyclohexylanisole, 125 ml. of acetic anhydride and 20 ml. oftrifluoroacetic acid is added dropwise at 10 C. to a solution of 0.16mole of iodine trifluoroacetate in 50 ml. of acetic anhydride. Thereaction mixture is stored in a refrigerator overnight and stirred atroom temperature for 3 hours. The solvents are evaporated in vacuo toleave a dark oil which is taken up in 400 ml. of methanol. The solutionis diluted with ml. of 10% sodium bisulfite and 500 m1. of watercontaining g. of potassium iodide. Addition of 125 ml. of etherprecipitates a yellow solid, bis(3-cyclohexyl-4-methoxyphenyl)iodoniumiodide, M.P. 167-168" C.

A mixture of 12.7 g. (0.02 mole) of this compound, 5.1 g. (0.01 mole) ofN-acetyl-3,5-diiodo-DL-tyrosine, ethyl ester. (J. Chem. Soc., 1950,2824), 1.5 ml. of triethylamine, 0.1 g. of activated copper in ml. ofmethanol is stirred at room temperature for 24 hours. The filteredsolution is evaporated. The residue is taken up in benzene then washedwith dilute hydrochloric acid. The precipitated amine salt is separatedand the filtrate washed with water, 10% sodium hydroxide and then water.The dried benzene solution is concentrated to a yellow oil. Triturationwith petroleum ether gives a white solid, N- acetyl-3-[4 (3-cyclohexyl-4methoxyphenoxy) 3,5-diiodophenyl-]-DL-alanine, ethyl ester, M.P. 143-144C.

A mixture of 4.1 g. of the ester, 25 m1. of hydriodic acid and 40 ml. ofacetic acid is heated at reflux for 5 hours, quenched and worked up asin Example 1 to give DL-3- cyclohexyl-3,5-diiodothyronine, M.P. 228230C.

Example 3 A mixture of 7 g. of N-acetyl-3,S-dinitro-DL-tyrosine ethylester, 45 m1. of pyridine, 4 g. of tosyl chloride and 3.5 g. of3-ethyl-4-methoxyphenol is reacted and worked up as in Example 1 to giveN-acetyl-3 [4-(4-methoxy-3- ethylphenoxy)-3,5-dinitrophenyl] DL-alanine,ethyl ester, M.P. 125-127 C. This compound is catalytically reduced anddiazotized in equimolar amounts as in Example 1 to giveN-acetyl-3-[4-(4-methoxy-3-ethylphenoxy)- 3,5-diiodophenyl]-DL-alanine,ethyl ester, M.P. 129-131" C. This intermediate (3 g. is hydrolyzed withhydriodic acid-glacial acetic acid by a one hour reflux period to giveDL-3-ethyl-3,5-diiodothyronine hemihydrate, M.P. 232234 C.

Example 4 Substituting equimolar quantities of o-tert. butylanisole foro-cyclohexylanisole of Example 2 gives the bis(3-tert.butyl-.4-methoxyphenyl)iodonium iodide, M.P. 177-178 C., thenN-acetyl-3-[4-(3-tert. butyl-4-methoxyphenoxy)- 3,5-diiodophenyl]-DL-alanine, ethyl ester, M.P. 137-139 C. and finally DL-3'-tert.butyl-3,5-diiodothyronine.

Example 5 ample 1 and working in the DL series gives the dinitrocompound, M.P. 173-175 C., the diiodo intermediate,

9 M.P. 128130 C. and finally DL-3'-phenyl-3,5-diiodo- Example 7Substituting o-isopropylanisole for ocyclohexylanisole in Example 2gives bis(3-isopropyli-methoxyphenyl) iodonium iodide, M.P. 14815G C. asWell as the other compounds with melting points as mentioned in Example5.

Example 8 L-3-isopropyl-3,S-diiodothyronine (500 mg.) is heated in 50ml. of 2% sodium carbonate solution until the mixture is clear. Coolingseparates the sodium salt. Another sample (250 mg.) is heated with 5%hydrochloric acid. The cooled solution gives the hydrochloride salt.

DL-3'-isopropyl-3,S-diiodothyronine (500 mg.) is dissolved in acetoneand reacted with hydrogen chloride to separate the salt. Another portion(250 mg.) is heated with dilute potassium carbonate to give thepotassium salt on cooling. Similarly the calcium salt is prepared.

What is claimed is:

1. A chemical compound of the formula:

I N I in which R is a branched acyclic alkyl group of from 3 to 7 carbonatoms.

3. L-3'-isopropyl-3,S-diiodothyronine.

4. DL-3'-isopropyl-3,S-diiodothyronine.

5. DL-3-cyc1oheXyl-3,S-diiodothyronine.

6. DL-3'-phenyl-3,S-diiodothyronine.

7. The sodium salt of L-3'-isopropyl-3,S-diiodothyronine.

8. The hydrochloride salt of L-3'-isopropyl-3 ,5-diiodothyronine.

References Cited in the file of this patent UNITED STATES PATENTS2,970,165 Michel et al Jan. 31, 1961

1. A CHEMICAL COMPOUND OF THE FORMULA: